Lionel Messi and nine other teammates look to have all but guaranteed a place in Barcelona's starting line-up ahead of the Champions League trip Chelsea on Tuesday (20 February) with Ernesto Valverde having only two enforced absentees in the form of the suspended Nelson Semedo and the cup-tied Phillipe Coutinho.

However, the former Athletic Club Bilbao boss still faces a dilemma over who to choose to play behind Messi and Luis Suarez in the middle of the park in his usual 4-4-2 formation.

At the beginning of the season it was expected that the Barcelona boss was going to continue with the 4-3-3 used by Luis Enrique with Ousmane Dembele covering the gap left in the attack by Neymar's departure to Paris Saint-Germain.

But the Frenchman has since struggled with different injuries and the 4-4-2 system with an extra man in midfield has emerged as Valverde's favourite formation.

Messi and Suarez are unmovable in the attack while Sergio Busquets, Ivan Rakitic and Andreas Iniesta have also been regular starters whenever they have been fit.

In defence, left-back Jordi Alba, Samuel Umtiti and Gerard Pique are also untouchable with the versatile Sergi Roberto having seen off competition from Nelson Semedo for the remaining place in the right-back.

So with Marc Andre Ter Stegen as the trusted Number one the biggest doubt is over who will occupy the remaining fourth place in the midfield when Barcelona visit Chelsea for the first leg of the Champions League last-16.

Andre Gomes, Paulinho and Aleix Vidal seem to be the most likely candidates with Dembele and Paco Alcacer among the possible alternatives if Valverde makes the rare decision to return to 4-3-3 formation.

1) Andre Gomes

Sport believes that the Portugal international will be the chosen one and the Spanish publication provide some good reasons to believe he will be given the nod.

Gomes was rested by Valverde during the weekend's 2-0 victory over Eibar and has not played since the second leg of the Copa del Rey semi-final against Valencia on 8 February.

The midfielder has struggled to make the impact expected since his arrival from Valencia but Valverde already started him in other key games this season, including the La Liga trip to Atletico Madrid and that the second leg semi-final with Los Che.

Andre

2) Paulinho

The Brazilian played against Chelsea during his unsuccessful time at Tottenham Hotspur and was selected by Valverde in midfield during the weekend's win over Eibar.

He has scored eight goals this season and was also in the starting line-up during the 3-0 victory over Real Madrid in the first El Clasico of La Liga on 23 December.

However, his introduction in the starting XI would see Barcelona forced into playing a diamond in midfield and Valverde might prefer to use someone who can play wider against Antonio Conte's 3-5-2 formation.

Paulinho

3) Aleix Vidal

The former Sevilla star was tipped to leave Barcelona during the recent January transfer window [Mundo Deportivo] but he has stayed and could earn promotion to face Chelsea if Valverde wants to use a genuine wing-back.

Vidal started the first leg of the Copa del Rey semi-final against Valencia and, given that he has also played in the right-back on occasion, he could help Sergi Roberto stop Chelsea's offensive threat through on left side from Marcos Alonso and Eden Hazard.

Vidal